1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus in which ultrasonic waves are transmitted into a subject, the ultrasonic waves reflected within the subject are received to obtain received signals, and an image is produced in accordance with the received signals. More particularly, the present invention relates to an ultrasonic diagnostic apparatus having a function of guiding a puncture needle to be introduced into a subject.
2. Description of the Related Art
Hitherto, there has been widely used for the purpose of diagnoses of a disease an ultrasonic diagnostic apparatus in which ultrasonic waves are transmitted into a subject, particularly, a human body, and the ultrasonic waves reflected at tissues within the subject are received to obtain received signals, so that an image is produced in accordance with the received signals thus obtained.
In some cases, it happens that for the purpose of picking of a part of tissues of the affected part for a diagnosis, while an image of the affected part within the subject, which is obtained with the use of the ultrasonic diagnostic apparatus as mentioned above, is observed, or for the purpose of injecting medical liquid into the affected part, a puncture needle is introduced into the affected part within the subject.
An ultrasonic diagnostic apparatus comprises, usually, an ultrasonic diagnostic apparatus main frame and an ultrasonic probe to be connected to the main frame. When a puncture needle is to be introduced into the subject, a guide member for guiding the puncture needle to be introduced into the subject is loaded onto the ultrasonic probe main body. The main body has a guide passage through which the puncture needle is introduced into the subject, so that the puncture needle is controlled by an operator in such a manner that it reaches a desired position while the operator observes an image of the seat of the disease.
The puncture needle is a hollow tube like an injection needle. For example, a tissue of the effected part is picked out through the tube of the puncture needle. The extracted tissue is submitted for a pathological examination and the like, and is used for a determination, for example, as to whether it is concerned with a malignant disease or a benign disease. Incidentally, while it was explained that the guide member is loaded onto the ultrasonic probe main body, it is acceptable that the ultrasonic probe main body and the guide member are formed into a unitary body. However, also in the following explanation, it will be continued assuming that the guide member is detachably loaded onto the ultrasonic probe main body.
FIG. 21 is a typical illustration of an ultrasonic probe in the state that a puncture needle is introduced into the subject. FIG. 22 is an illustration of an image by means of ultrasonic waves in such a state.
An ultrasonic probe 20 comprises a main frame 21 and a guide member 22 which is detachably loaded onto the main frame 21. On the tip of the main frame 21, there is arranged a plurality of ultrasonic transducers 211 (e.g. 128 pieces) as a circular arc by way of example. The ultrasonic transducers 211 are connected through a cable 212 to an ultrasonic diagnostic apparatus main frame (not illustrated).
To obtain an ultrasonic image, the tip of the ultrasonic probe 20 is put to the subject 1 so as to sequentially perform a transmit-receive operation for ultrasonic beams along a plurality of scanning lines 2 each extending from the tip of the ultrasonic probe into the subject 1. In this manner, a scan of the inside of the subject by a series of transmit-receive operations for ultrasonic beams makes it possible to obtain received signals representative of an ultrasonic image within a scanning area 3 defined by the plurality of scanning lines 2. The received signals thus obtained are subjected to various types of processing and then transmitted to an observation monitor television (not illustrated), so that the associated image within the scanning area 3 is displayed on a display screen 707a (cf. FIG. 22) of the observation monitor television.
To introduce a puncture needle 30 into the subject, the guide member 22 is loaded onto the main frame 21. As shown in FIG. 22, on an image screen, there is displayed a diagram 30a representative of a passage of the puncture needle 30, with being superposed on the image within the scanning area 3. The ultrasonic probe 20 is controlled in its position and direction to be put to the subject 1 so that an affected part 11 to which the puncture needle 30 is intended to be introduced and the diagram 30a indicative of the passage of the puncture needle 30 intersect. Under such a control of the ultrasonic probe 20, the puncture needle 30 is introduced into the subject 1 along a guide passage 22a of the guide member 22. In this manner, it is possible to introduce the puncture needle 30 into a desired position within the subject with a certain degree of reliability. Incidentally, in the above-description, while it was explained that the diagram 30a indicative of the passage of the puncture needle 30 is displayed on the display screen 707a, there is an ultrasonic diagnostic apparatus having no such a display function for the diagram.
When it is practiced such a puncture technique that a puncture needle is introduced into the subject to pick out tissues within the subject or inject a medical liquid into tissues within the subject, a low resolution of an image makes it difficult for an operator to exactly grasp a position of the puncture needle inserted into the subject. Further, it is difficult to adjust the tip of the puncture needle to a desired small point of the affected part 11. This is one of causes which make it difficult to exactly perform the puncture technique. Furthermore, even if there is displayed on the image screen a diagram indicative of the passage of the puncture needle, it happens that the puncture needle travels with being curved somewhat at the boundary of tissues within the subject, and thus the puncture needle does not always travel as indicated by the diagram. For these reasons, it is necessary to exactly grasp a position of the puncture needle indeed inserted into the subject. In the event that a position of the puncture needle cannot be exactly grasped, this is in danger of injuring blood vessels, internal organs or the like other than the site to which the puncture needle is intended to be introduced.
In order to solve these problem, there has been proposed a scheme in which a predetermined image area, which is located along a guidance direction for the puncture needle, is subjected to an image processing different from that for other image area, whereby it is easy to see the puncture needle on the image screen (cf. Japanese Patent Application Laid Open Gazette Sho. 63-290550).
The above-mentioned scheme fails to propose a solution as to what image processing is practiced to easily to see the puncture needle, although it is understood as to such a requirement that the puncture needle is displayed so as to be easy to see. Even if the puncture needle is displayed so as to be easy to see in accordance with the image processing, in order that the puncture needle reaches a desired point without injuring blood vessels, internal organs or the like other than the site to which the puncture needle is intended to be introduced, it is insufficient that only the puncture needle is displayed so as to be easy to see, and it is necessary to display also images of other than the puncture needle, for example, blood vessels, internal organs or the like within the subject.
Hitherto, there have been developed and proposed various types of image processings in which both the puncture needle and the blood vessels, internal organs or the like within the subject are subjected to an image processing in such a manner that they are easiest to see in the earlier technology of the field of the image processing. However, there remains such a problem that the position of the puncture needle is difficult to be grasped. Accordingly, the above-mentioned scheme such that the passage area of the puncture needle and another area are simply differentiated from each other in an image processing cannot implement an image which permits the position of the puncture needle to be exactly grasped, and also permits the puncture needle to reach a desired point without injuring blood vessels, internal organs or the like other than the site to which the puncture needle is intended to be introduced.
An image for an observation is usually determined in its resolution (e.g. density of scan lines 2 shown in FIG. 21) in view of the frame rate as an index indicative of the number of sheets of images capable of being obtained per unit time. To perform a puncture technique, there is a need to provide an image having a higher resolution than that of the image for an observation, and thus the image for an observation is essentially insufficient in its resolution. On the other hand, if it is intended that the resolution of the image is enhanced, then the frame rate will be decreased, since the resolution is determined in view of a balance with the frame rate, as mentioned above. As a result, a change of images cannot follow a velocity at which the puncture needle is introduced into the subject. This involves a problem which makes it difficult to perform a puncture technique with accuracy in the point of the frame rate.
Further, there is proposed such a technology that a tip portion of a puncture needle is vibrated by an oscillator to pick up a variation of the signals by a vibration, thereby exactly detect the tip position of the puncture needle (cf. U.S. Pat. No. 5,095,910). Specifically, according to the technology disclosed in U.S. Pat. No. 5,095,910, the tip position of the puncture needle is detected in such a manner that a Doppler transition of a frequency of ultrasonic waves reflected on the tip of the puncture needle, which occurs owing to the vibration of the tip of the puncture needle, is detected.